Marauder is one of the five skins released under the Radioactive offer. It could be individually purchased with game coins in October 2016.
Mutant could be purchased in the Skins Shop under the ‘Nuclear’ tab for 4900 coins. This skin was available for a limited time and may not be available for purchase in the future.
Details of this skin can vary depending on location, platform or time.
Note: The Radioactive offer with the Mutant skin was released again for a limited time in early February 2019. The price for Mutant remained the same at 4900 coins.